Tree-crop Interaction as Affected by Tree Spacing and Pruning Management in Bangladesh

Abstract

Due to massive deforestation, growing of trees in the crop field and homestead area to increase forest cover is deemed necessary. Data on proper spacing and pruning management of tree species are meagre. Acacia nilotica and Albizia lebbek agroforestry systems gave the highest yield of mustard (0.431 and 0.788 t/ha respectively) and rice (2.89 and 2.50 t/ha respectively) compared to other local tree species in the farmers' crop field. Grain yields of rice and wheat were lower in spacing treatment of Acacia nilotica than that in the open field. The spacing of 12m x 1m had the highest grain yields of rice and wheat in 1990 (2.18 and 2.32 t/ha respectively) and in 1992 (0.48 and 0.86 t/ha respectively) on field area basis. Root pruning treatment of A. nilotica contributed to the highest grain yield of wheat (1.87 t/ha) at 12m x 1m spacing, which was comparable to open field system (2.18 t/ha). Root pruning treatment showed lower gross margin (US $424/ha) compared to root unpruned (US $460/ha) because of higher cost involvement for digging. Another study revealed that shoot pruning of trees thrice a year had the highest significant positive effect on the crop yield where 71% radish (vegetable) yield was increased with Acacia nilotica, and 50% rice and 55% radish yields were increased with Albizia lebbek. Shoot pruning of Acacia twice a year was found more efficient to enhance rice yield by 27%. Shoot pruning of Albizia and Acacia thrice a year contributed the highest fuelwood (5.27 t/ha/year and 7.16 t/ha/year respectively). Moreover, it was also observed that the shoot pruning significantly enhanced the lateral growth (increase in tree girth) of both the species and the highest value was achieved with pruning thrice a year (30mm in Acacia and 26.7mm in Albizia over 8 months). Highest additional margin of US $ 450/ha and US $ 544/ha in 2 crop seasons were recorded with prunipg thrice a year in Acacia and Albizia systems respectively at an additional cost of US $ 113.